Automatic alignment of a contrast enhancement system

ABSTRACT

An apparatus and method for insuring the proper alignment of a detected vein pattern and a projected vein pattern are disclosed. The apparatus enhances the visual appearance of veins so that an error that can lead to improper patient care or injury can be avoided.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/121,668, filed Sep. 5, 2018, which is a continuation of U.S.application Ser. No. 15/665,504, filed Aug. 1, 2017, now issued as U.S.Pat. No. 10,096,096, which is a continuation of U.S. application Ser.No. 15/226,027, filed Aug. 2, 2016, now issued as U.S. Pat. No.9,760,982, which is a continuation of U.S. application Ser. No.14/196,172, filed Mar. 4, 2014, now issued as U.S. Pat. No. 9,430,819,which is a continuation of U.S. application Ser. No. 12/215,713, filedJun. 27, 2008, now issued as U.S. Pat. No. 8,730,321, which claimspriority on U.S. Provisional Application Ser. No. 60/937,618, filed Jun.28, 2007, all disclosures of which are incorporated herein by reference.

SUMMARY OF THE INVENTION

An apparatus and method for insuring the proper alignment of a detectedvein pattern and a protected vein pattern in a apparatus that enhancesthe visual appearance of veins so that an error that can lead toimproper patient care or injury can be avoided.

BACKGROUND OF THE INVENTION

It is known in the art to use an apparatus to enhance the visualappearance of the veins and arteries in a patient to facilitateinsertion of needles into those veins and arteries as well as othermedical practices that require the identification of vein and arterylocations. Such a system is described in U.S. Pat. Nos. 5,969,754 and6,556,858 incorporated herein by reference as well as publicationentitled “The Clinical Evaluation of Vein Contrast Enhancement”.Luminetx is currently marketing such a device under the name “VeinviewerImaging System” and information related thereto is available on theirwebsite, which is incorporated herein by reference.

The Luminetx Vein Contrast Enhancer (hereinafter referred to as LVCE)utilizes a light source for flooding the region to be enhanced with nearinfrared light generated by an array of LEDs. A CCD imager is then usedto capture an image of the infrared light reflected off the patient. Theresulting captured image is then digitally enhanced and then projectedby a visible light projector onto the patient in a position that must beclosely aligned with position of the captured image. The practitioneruses this projected image to determine the position in which to insert aneedle. Should the image be misaligned, the patient can be injured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an embodiment of a vein contrast enhancer.

FIG. 2 is a representation of a patient's arm.

FIG. 3 shows an embodiment of a laser contrast enhancer.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, a typical embodiment of a vein contrast enhancer(VCE) 100 contains a camera 101 which is used to capture an image of apatient's body 105, a processing system (not shown) that enhances theimage captured by the camera to highlight the positions of veins, and aprojector 102 that shows an image of the enhanced vein pattern back ontothe patient's body 105. Since the camera and projector are physicallyseparate devices they reach the patient's body from different sourcepoints along different paths 103, 104. In some embodiments, the pathsare made coaxial within the body of the VCE, however at some point thepaths are separate since the devices (camera and projector) arephysically separate devices. Since the purpose of a VCE is to allow thepractitioner to insert a needle into the highlighted vein, it iscritically important that the projected image and the actual veinlocation be aligned. Typically this alignment is done as a separate stepin the use of the VCE. A card with a known pattern is placed with theviewing/projecting field of the VCE. This card has florescent materialapplied to it so that when it is struck by green light, it emitsinfrared light that can be seen by the camera. This image is used toalign the VCE.

This invention describes methods for achieving this alignment withoutrequiring the operator to take a separate step.

Referring to FIG. 2, a representation of the patient's arm 201 is shownalong with several veins. A bounding box is shown around a single vein200. In FIG. 3, a schematic representation of the bounded area of thesingle vein is shown 305. Typically, the enhancement image will light upthe area around the vein and will be dark on the vein. When properlyaligned, the bright part of the image 300 will have edges that properlyalign with the edges of the veins 303, 304. As previously described, theVCE will typically have an alignment mode wherein a known pattern,typically presented on an alignment card, will be placed in front of theVCE and an alignment will be performed. This alignment can either beautomatically performed by the VCE or manually performed by theoperator. The weakness of this kind of implementation is that is relieson the expectation that the alignment will be maintained overtime. Ifthe alignment should shift, patient injury can occur.

In a typical VCE, an infrared light source and a camera that issensitive only to infrared light is used to detect the vein position.Furthermore, the projected image is often green in color to insure thatthe light from the projector is ignored since the camera is sensitiveonly to light near the infrared region. This selectivity can beimplemented either with filters or with selectively sensitive cameraelements.

Referring back to FIG. 3, in a typical LCE, the camera, by design, isblind to this projected light. In our invention, the camera is bydesign, able to selectively see the projected light. In a preferredembodiment, a multi-color capable projector is used. As usual, green isused to fill the area outside of the vein 300. That green projectiongoes to the edges of the vein position 303, 304 and the vein area itselfis left dark. A camera that is sensitive to red and infrared light isused in this embodiment. In addition to the green fill, red lines aredrawn at the edges of the veins 303, 304. Since the camera can see thesered lines, the image enhancement software can look to see if the redlines are at the proper position and if needed automatic alignment canbe performed. An alternative embodiment would be to paint a red line 306down the middle of the vein position. An alternative embodiment would beto paint some patter of red light over a desired portion of the vein.

Typically the cameras used in an LCE are monochrome and unable todiscriminate between light of different wavelengths. Depending on thesensitivity of the camera and the brightness of the projector comparedto the infrared flood lighting provided by the LCE, various techniquescan be used to aid the camera in the detection of the red lines. Onemethod is to simply look for the brightening caused by the addition ofthe red lines to the reflected infrared light. A second method is toperiodically turn off the infrared lighting such that only ambientinfrared and the projected red are seen by the camera. This can make iteasier for the system to detect the red lines.

Although we've described the invention using red and green lights,various combinations of colors can be used. Red and infrared light areknown in the art to be useful for vein detection. Any combinations ofcolors of shorter wavelengths can be used for projection and alignmentimages as long as the camera selected is properly selected or filteredto achieve the desired discrimination between wavelengths. Furthermore,while discrimination between projection, detection and alignment signalsin the preferred embodiment has been described using differentwavelengths to separate the signals, in an embodiment with less freedomof projected color, time division can be used where the projected imageis shown most of the time and the alignment image is shown interspersedon a lower duty cycle basis. Properly implemented, the alignment imagewill be quite visible to the VCE's camera, but invisible to the operatorof the VCE. Projectors in VCEs can be either monochrome (e.g.,projecting green only) or multicolor (e.g., projecting RGB). Theadvantage of a monochrome implementation is that since an array ofsingle color LEDs can be used in place of white bulbs and a color wheeltypically found in a multicolor projector the system can be of lowercost, generate less heat and have higher reliability. In such anembodiment, the time division scheme describe above would beappropriate. In this monochrome configuration, an alternative embodimentwould be to add a smaller array of a second color of LEDs (i.e., red).This alignment array can be smaller than the projection array in that itdoesn't need to be visible to the operator, just to the camera. Theprojection LEDs and the alignment LEDs could then be time multiplexed aspreviously described.

We claim:
 1. A vein imaging system comprising: a light source thatilluminates a field of view with a first wavelength of light comprisingan infrared wavelength, to create an image contrast of one or more veinsformed by differential amounts of absorption and reflection of saidfirst wavelength of light by the one or more veins and surroundingtissue in the field of view; an alignment card comprising a patternformed of a material that emits a second wavelength of light whenexposed to a third wavelength of light; a camera configured to capturesaid image contrast of the one or more veins at said first wavelength oflight; a projector configured to receive and to project said capturedimage contrast onto the field of view using said third wavelength oflight; wherein said camera is further configured to capture said secondwavelength of light emitted by said pattern when positioned in the fieldof view, and to capture said third wavelength of light reflected fromsaid pattern, said camera further configured to distinguish said thirdwavelength of light reflected by said pattern, from said secondwavelength of light emitted by said pattern; and an image processorconfigured to align said projection of said image contrast with saidimage contrast formed by the differential absorption and reflection,using said distinction between said captured reflection of said patternat said third wavelength of light, and said captured emission from saidpattern as said second wavelength of light.
 2. The vein imaging systemaccording to claim 1 wherein said pattern comprises a fluorescentmaterial.
 3. The system according to claim 1 wherein said patterncomprises a known pattern.
 4. The vein imaging system according to claim1 wherein said third wavelength of light comprises a human visiblewavelength of light.
 5. The vein imaging system according to claim 1wherein said third wavelength of light comprises a green wavelength oflight.
 6. The vein imaging system according to claim 5 wherein saidsecond wavelength of light comprises a red wavelength of light.
 7. Thevein imaging system according to claim 6 wherein said green wavelengthof light of said projected image contrast is projected onto the field ofview outside of the one or more veins.
 8. The vein imaging systemaccording to claim 1 wherein said third wavelength of light and saidinfrared first wavelength of light are alternately projected andilluminated, respectively.
 9. The vein imaging system according to claim8 wherein said third wavelength of light is projected at a higher dutycycle than said illumination with said infrared wavelength.
 10. A methodof aligning a projection of an image of subcutaneous veins with theimaged veins, said method comprising: illuminating a field of view witha first wavelength of infrared light; capturing the first wavelength ofinfrared light reflected from the field of view as an image contrastformed by differential absorption and reflection by the veins andsurrounding tissue therein; forming an alignment card using a materialconfigured for emitting a second wavelength of light when exposed to avisible light at a third wavelength; positioning the alignment card inthe field of view; projecting the captured image contrast onto the fieldof view using the visible light at the third wavelength; capturing thesecond wavelength of light emitted by the alignment card, and thevisible light at the third wavelength reflected from the alignment card;determining a positional difference between the captured secondwavelength emitted from the alignment card and the captured reflectionof the projected alignment card at the third wavelength; and aligningsaid projecting of said captured image contrast according to saidpositional difference.